The present invention relates to a medical oxygen-concentrating equipment for separating oxygen from air and producing the oxygen-concentrated air. In more detail, the invention relates to an oxygen-concentrating equipment in which a humidifying means using a solid electrolyte membrane to humidify the oxygen-concentrated air is installed, and to the medical oxygen-concentrating equipment with which a user can continuously inhale oxygen without supplying water.
A medical gas including oxygen is supplied in the form of a compressed gas in a cylinder, a liquefied gas in a cylinder or direct supplying from a purifying-concentrating equipment. Among them, the concentrating equipment includes equipments based on a low temperature processing method, equipments based on a membrane separation method using a membrane permitting the preferential penetration of only a specific gas component, and equipments based on an adsorption method using an adsorbent such as zeolite. However, as the oxygen-concentrating equipments used in hospitals or by patients at their homes, the equipments based on the adsorption method, especially a pressure swing adsorption method that the inner pressure of an adsorption cylinder filled with a nitrogen-adsorbing agent based on zeolite is continuously changed to carry out adsorption and reactivation operations, are dominant.
The adsorbent used for the pressure swing adsorption method includes zeolite and molecular sieve carbon, but the equipment using 5A type or 13xc3x97 type zeolite is a leading one as the oxygen-concentrating equipment. These zeolites have properties for more preferentially adsorbing nitrogen than oxygen. When air is charged into the cylinder in an adsorption process, only nitrogen is selectively adsorbed to leave oxygen as a gas phase component, and the left gas is taken out to obtain the oxygen-concentrated air.
Furthermore, these zeolites have a property for adsorbing water stronger than oxygen and nitrogen. When the water is contained in air, the zeolite adsorbs the water, and the nitrogen-adsorbing capacity of the zeolite is thereby reduced to cause the deterioration of the adsorbent. When the oxygen is concentrated by the pressure swing adsorption method using the zeolite, it is therefore preferable that the air used as the raw material is in a state that the water is removed as much as possible.
On the other hand, the oxygen purified with the above-mentioned pressure swing type adsorption equipment is in an absolutely dry state that water is nearly perfectly removed by the water-absorbing property of the zeolite. When a patient inhales the absolutely dry medical gas, troubles such as the decrease in the ciliary movement of an upper respiratory tract mucous membrane, the loss of water and calorie in the body and the difficulty of expectoration due to the dryness of sputum are caused. It is therefore necessary that the medical gas is preliminarily humidified with a humidifier or the like, before the patient inhales the medical gas.
Conventionally, the humidifiers based on a method that the product oxygen gas is passed through purified water placed in a container, and based on a method that the oxygen is passed through water in a bubble state, have been often used as humidifiers for humidifying the product oxygen gas. However, since using the water, the humidifiers have problems, for example, the necessity of maintenance such as the periodical supply or exchange of the water because of the propagation of bacteria on the employment of the humidifiers for long periods, and the abnormal supply of the product oxygen gas due to the failure of reassembly on the maintenance.
As one of methods for solving the problems, a method, comprising using a water-transferring membrane, allowing raw material air to flow on one side of the membrane to transfer oxygen to the other side, simultaneously transferring moisture in the raw material air to the product oxygen by the utilization of a steam partial pressure difference, thereby dehumidifying the raw material air and simultaneously humidifying the oxygen, such as an invention described in JPA 2-99113 (1990) (hereinafter, JPA means Japanese Unexamined Patent Publication), is known. Since the humidification degree of the oxygen largely depends on the humidity of the raw material air, the method has the following problems. For example, when the humidity of the raw material air is low, the oxygen is sufficiently not humidified, while when the humidity is high, the oxygen is excessively humidified, thus forming dew on the inner surface of piping and giving unpleasantness to a patient on his inhalation of the moisture in the form of liquid water.
In addition, a method comprising by-passing the water transfer membrane with disposing a by-pass on a piping for the raw material air or the product oxygen, in such oxygen-concentrating equipments described in JPA 5-49697 (1993) and JPA 8-196635 (1996), has also been considered for controlling the humidification degree. However, the method has problems such as the complication of the piping and the complication of a control mechanism due to a necessity for controlling the valve aperture of the by-bass for the control of the humidification degree.
Recently, a dehumidifier using a cation-conducting solid polymer electrolyte, as described in JPA 0-223220 (1998), was proposed. The dehumidifier has a basic structure having a cathode on one side of a cation-conducting solid polymer electrolyte and an anode on the other side, as shown in FIG. 6, and utilizes the following reactions:
on the side of the anode:
2H2Oxe2x86x92O2+4H++4exe2x88x92
on the side of the cathode:
O2+4H++4exe2x88x92xe2x86x922H2O
which are generated on the anode and the cathode, when an electric current is applied. The dehumidifier using the solid polymer electrolyte has a defect which comprises producing a dry air layer in the neighborhood of the anode side membrane surface of the solid polymer electrolyte membrane to prevent the supply of wet air to the membrane surface and thereby significantly deteriorating the humidifying capacity of the solid polymer electrolyte membrane, when continuously used.
The object of the present invention is to provide an oxygen-concentrating equipment installed with a humidifying means, which can dissolve the problems of conventional equipments, does not need periodical maintenance such as the supply of water, can continuously give a sufficient humidification degree, and enables the free and easy setting of the humidification degree.
The present inventor zealously examined the problem, and consequently found out the following oxygen-concentrating equipment.
Namely, the present invention is to provide the oxygen-concentrating equipment comprising an oxygen-concentrating means for separating oxygen from air to concentrate the oxygen, a humidifying means for humidifying the oxygen-concentrated air produced by said oxygen-concentrating means, and an oxygen-supplying means for supplying the humidified oxygen-concentrated air to a user, characterized in that said humidifying means has at least a cation-conducting solid electrolyte membrane equipped with electrodes on both the sides of the membrane and an electric source for applying an electric current to said electrodes.
Furthermore, the present invention is to provide the oxygen-concentrating equipment, characterized in that said humidifying means is a means which has, on the anode side, a catalyst layer for electrolyzing water molecule into oxygen molecule and hydrogen ion and has, on the cathode side, a catalyst layer for producing water molecule from the oxygen molecule and the hydrogen ion.
Furthermore, the present invention is to provide the oxygen-concentrating equipment, characterized in that said oxygen-concentrating means is a pressure swing adsorption type oxygen-concentrating means which has an adsorption cylinder filled with an adsorbent adsorbing nitrogen more selectively than oxygen and a compressor for supplying compressed air to said adsorption cylinder, and said humidifying means has a flow path to flow raw material air, to be supplied to said compressor, on an anode side and a flow path to flow the oxygen-concentrated air, produced by said oxygen-concentrating means, on a cathode side.
Furthermore, the present invention is to provide the oxygen-concentrating equipment, characterized in that said oxygen-concentrating means is a pressure swing adsorption type oxygen-concentrating means which has an adsorption cylinder filled with an adsorbent adsorbing nitrogen more selectively than oxygen and a compressor for supplying compressed air to said adsorption cylinder, and said humidifying means has a flow path to flow cooling air on an anode for cooling the inside of said oxygen-concentrating equipment and a flow path to flow the oxygen-concentrated air, produced by said oxygen-concentrating means, on a cathode side for allowing.
Furthermore, the present invention is to provide the oxygen-concentrating equipment, characterized in that said oxygen-concentrating means is a pressure swing adsorption type oxygen-concentrating means which has an adsorption cylinder filled with an adsorbent adsorbing nitrogen more selectively than oxygen and a compressor for supplying compressed air to said adsorption cylinder, and said humidifying means has a flow path to flow the air desorbed from the adsorption cylinder on an anode side and a flow path to flow the oxygen-concentrated air, produced by said oxygen-concentrating means, on a cathode side.
Furthermore, the present invention is to provide the oxygen-concentrating equipment, characterized in that a control means, for controlling the electric current value and/or voltage value of an electric current applied from said electric source to said electrodes, is installed and in that a control means, for controlling the electric current value and/or voltage value of an electric current applied from said electric source to said electrodes so that the electric current value and/or voltage value do not exceed the upper limits, is installed.
Furthermore, the present invention is to provide the oxygen-concentrating equipment, characterized in that a humidity-measuring means, on the cathode side of said humidifying means or in the downstream on the cathode side of said humidifying means, is installed and a control means, for controlling said measuring means so that the measurement value of said humidity-measuring means is equal to a set value, is installed and in that a control means, for calculating the transfer rate of water on the basis of the flow rate value and temperature value of the oxygen-concentrated air flowing on the cathode side of said humidifying means and then controlling said control means, is installed.